Reinforced sods have long been known in the art. Sod mats of groundcovers, flowers, and playing field grasses are among the examples.
Molnar (U.S. Pat. No. 5,224,290) discloses flower and groundcover sod mats reinforced with nylon sod reinforcements. Decker (U.S. Pat. No. 4,986,026) discloses tall fescue sod mats which are very large and employ planting mediums containing straw and sewage sludge. Molnar (application Ser. No. #07/745224) discloses flower and groundcover sod mats reinforced with polypropylene sod reinforcements. Milstein (U.S. Pat. No. 4,941,282) discloses wildflower sod mats reinforced with polyester fabrics. McFarland (U.S. Pat. No. 4,786,550) discloses a lightweight seed mat formed with melt blown nonwovens. Walton (U.S. Pat. No. 4,934,094) discloses a grass sod reinforced with netting. Decker (U.S. Pat. No. 4,336,668) discloses a novel method of growing groundcover sods reinforced with synthetic netting. Muldner (U.S. Pat. No. 4,190,981) discloses a complex lightweight seed mat using complex expensive equipment. Airhart in HortScience 18(1), 89-91, 1983 discloses groundcover and flower sods reinforced with synthetic netting.
In general, sod mats reinforced with synthetic spunbond nonwoven fabrics are excellent all purpose sod mats. They have very good sod mat production characteristics, good strength and are easy to handle. They may, however, have special hydrophilic treatments or particular chemistries to promote good water infiltration and root wetting. The particular hydrophilic treatments add complexity and cost to manufacture. In addition, in some cases the hydrophilic treatment does not last as long as desired. Furthermore, one must be sure any hydrophilic treatments which leach out do not have an adverse impact on the environment. Often, nonwoven chemistries which are naturally hydrophilic are also generally more expensive and thus also increase cost.
Sod mats employing natural reinforcements such as straw, bark, or water sensitive glues can decompose prematurely if harvest time is delayed or if the planting medium is particularly biologically active.
Sod mats reinforced with synthetic netting have excellent water infiltration characteristics but have certain limitations. If the netting openings are large, harvest is usually delayed, while if the netting openings are small, the roots of the specialty plants can be girdled. Neither leads to sod mats with both optimum sod mat production and growing characteristics. If the netting openings are large, the netting can also be troublesome to completely cover with planting medium.
In view of the above background art, there still exists a need for modified sod mats which combine the advantages of early harvest time, good "shelf life" stability, versatility, good long term water infiltration characteristics and which promote root wetting, are easy to handle and propagate, and are easy and inexpensive to manufacture. Reduced water runoff combined with improved water infiltration and root wetting have particularly high utility on highly sloped landscape applications. Objects of the current invention are then to develop a select group of preferred modified sod mats along with their method of manufacture which combine the advantages of early harvest time, good "shelf life" stability, versatility, and have good long term water infiltration characteristics, promote good root wetting, are easy to handle and propagate, and are also economical to propagate. It is a further object of the invention to minimize or eliminate the need for relatively expensive and complex hydrophilic treatments for low cost nonwoven sod reinforcements. Another object of the current invention is to minimize or eliminate any environmental contamination possibilities from hydrophilic treatments. Another object of the present invention is develop modified sod mats based on nonwoven sod reinforcements which are easy to recognize as having good water infiltration and root wetting without having to resort to time consuming or expensive chemical testing for hydrophilic treatments or chemical testing of the nonwoven fabric. In addition, another object of this invention is to develop a manufacturing process for these modified sod mats with good sod mat production characteristics.
Other objects and advantages of the current invention will become more apparent to those skilled in the art in view of the following description and examples.